I wonder what the tolerances are on the dumbbells at my gym. I've been assuming that the reason the 12.5-pound ones feel that much harder than the 10-pound ones is that 10 is my comfortable range, what I use most of the time for that exercise, and 12.5 is pushing it. (And some days I step down to 7.5, if it's that or not do biceps curls at all.)

And I wonder how weirdly they'd look at me if I told this story and asked if they've ever checked the weights of the freeweights.

(I know that "levels" on the exercise bikes are arbitrary and not consistent across models; I also suspect that the heart rate measurements aren't reliable.)